本研究は, トポロジカル超流動体としての新展開が期待される超流動ヘリウム3に対して, ジョセフソン効果および準粒子トンネル分光, 集団励起などの実験を行い, トポロジカル性を検証し新奇状態を探索するものである。
AB両相でトポロジカル超流動の特徴的性質発現が期待される擬2次元薄膜を実現するため, シリコンウェハー貫通スリット構造とスラブ円盤空間の作製を進め, 前者については幅2×100μmの貫通スリット, 後者は1μm高さに対し平坦度乱れが4nmという極めて平坦な円盤空間の作製に成功した。また超流動流測定装置, 超音波実験装置, ねじれ振動子装置の開発を行った。同時に製作した核断熱消磁冷凍機を用いて実験を行う。
In this project, we study topological properties of superfluid 3He by performing experiments on Josephson effect, quasiparticle transport, and collective excitations. We have attempted to fabricate novel microslit structures on Si wafers with dimensions 1x100μm by dry etching, and make a microslab structures by ultrahigh precision machining. So far we have succeeded to fabricate 2x100μm slit structures and 1μm thick disk-shape geometry with 4nm flatness. We have also prepared an apparatus to detect Josephson and quasiparticle flow using SQUID based displacement sensor, a ultrasound cell to study collective modes, and a torsional oscillator to search for chiral edge current. These devices are installed on a PrNi5 nuclear demagnetization refrigerator, which has also been prepared in this work. Some preliminary experiments have already been performed and experiments with superfluid 3He get underway.
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